Integrated circuit (IC) devices can typically include power-on reset (POR) circuits. Conventional POR circuits generate a pulse as a power supply voltage rises from a low level to a high level (i.e., ramps-up). Such a pulse can be used to signal that a power supply voltage for a device (e.g., integrated circuit) is sufficiently high enough to begin initializing other circuits or applying power to other circuits in order to start standard operations.
In addition to POR circuits, which can detect power-on/reset events, devices can also include “brown-out” detection (BOD) circuits. BOD circuits can detect brown-out conditions of a device. A brown-out condition can occur when a high power supply voltage falls below a predetermined level (i.e., a level at which a device may no longer operate as desired, or cannot be guaranteed to operate as desired).
FIG. 9 is a block schematic diagram of a conventional POR circuit 901. POR circuit 901 can include a voltage sense section 903, and series connected inverters 905-0/1/2. Voltage sense section 903 can include a capacitance C91, a discharge path M91, and a resistance R91. Capacitance C91 can be connected between a node A and a low power supply voltage (VSS). Discharge path M91 can be a transistor having a source connected to a high power supply voltage VCC, and a gate and drain connected to node A. Resistance R91 can be connected between VCC and node A. Inverter 905-0 has an input connected to node A, and an output (node B). Inverters 905-1/2 are arranged in series with inverter 905-0 and provide outputs shown as node B and a RESET signal, respectively.
During a fast ramping of VCC, node A can rise, but at a rate delayed with respect to VCC. As a result, inverters 905-0 to -2 can initially drive RESET signal high, starting a POR pulse. Once node A rises higher than a threshold voltage of inverter 905-0, inverters 905-0 to -2 can drive RESET signal low, ending a POR pulse.
However, during a slower ramping of VCC, there may not be sufficient delay between node A and VCC, and as a result, conventional POR circuit 901 may not generate a pulse. This can be remedied by increasing a size of resistance R91 and capacitance C91, but such a solution can require undesirably large amounts of circuit area and so be impractical for some designs.